1. Technical Field
The present disclosure relates to power supply circuits, and particularly to a power supply circuit for adjusting time sequence of a power good signal provided to a south bridge chip.
2. Description of Related Art
With the rapid development of personal computers, more functionalities are being added to the motherboard resulting in increase of power usage. Typically, the computer can automatically go into a sleep mode when not in use, and a wake up circuit is provided in power management to awake the computer. A sleep/wake button is usually provided on the keyboard of the computer that is connected to the inner wake up circuit of the motherboard of the computer. The button is pressed by a user for switching between the sleep and normal functioning modes.
When the computer is awakened from the sleep mode, components on a motherboard of the computer are powered up. During the power up sequence of the motherboard, there is a plurality of signals (e.g., power good signal, +5V_DUAL voltage signal, +5V_STBY voltage signal, +3.3V_DUAL voltage signal) in the computer that should meet a required signal time sequence. Typically, the south bridge chip is used for waking up the computer. A power supply circuit is used for providing power to the south bridge chip. The typical power supply circuit converts the +5V_DUAL voltage signal to the +3.3V_DUAL voltage signal by a voltage regulator on the motherboard to provide power for the south bridge. However, the typical power supply circuit has a low response speed, and the +5V_DUAL voltage signal is usually asynchronous with the power good signal during its rising up from low voltage level to high voltage level, which commonly causes the wake up circuit to fail.